Displays are applied abundantly in the daily life accompanying with the technology development, especially in the LCD. Since the liquid crystal molecule is a non-self-luminous substance, the function of display is achieved by the light supplied by the backlight module. At present, the cold cathode fluorescent lamp (CCFL) is commonly applied as the light source of the backlight module, and is cooperated with the structures, such as the liquid crystal molecule and the color filter, etc., to display the color image. However, comparing with the CCFL, the advantages of using LED array as the LCD backlight source lies in: (a) fast reaction rate, (b) long life-span, (c) without high-voltage lighting, (d) without mercury, no environmental pollution problem, and (e) wider color range. At present, although many companies make effort at developing CCFL with low mercury and wider color range, the reaction rate of the CCFL is the uneasily improvable disadvantage. Therefore, using LED as the LCD backlight source must be the developmental trend in the future. Nowadays, a novel display technology, area control or regional control, needs the backlight source of fast reaction rate in order to increase the contrast ratio of light and shade of the display. The emitting mode of the area control is described below.
In the traditional display technology, the brightness of the backlight lamps are identical, and the degree of light and shade of the screen is controlled by the tilted angles of the liquid crystal molecules. However, the method can't avoid the phenomenon of light leak. The screen is sectionalized into several areas by the area control, and the brightness of the backlight source is adjusted according to individual degree of light and shade. The backlight lamp with darker area of the screen is adjusted to darkness in order to decrease the phenomenon of light leak; therefore, the contrast ratio of light and shade of the display is increased enormously, and the power consumption of the backlight lamp is decreased at the same time. If the area control display technology are adopted, the speed of response of the backlight lamp must be increased as fast as possible so as to shorten the transient time and then increase the accuracy of the brightness. Therefore, the LED is very suitable for the backlight source of the area control display technology.
The color light mixing with the red, green and blue light LED arrays has a better scope of the color display. And, a display technology named sequential color display (SCD) method had been developed in recent years, the red, green and blue lights are sequentially generated by the backlight lamps. The colored screen is showed by the panel without cooperating with the color filter, and the power and the cost are decreased enormously. The control integrated circuit (IC) of the area control driving circuit of the present invention is cooperated with the single-set white LED backlight lamp, or cooperated with the LED backlight lamp of the red, green, and blue lights, and the LED backlight lamp of the sequential color display method.
Please refer to FIG. 1, which is a circuit diagram showing an area control driving circuit of the LED backlight lamp according to the prior art. It is configured by the backlight module 100 and the control center 700. Due to achieving the area control of the backlight lamp, the backlight lamps in each area must be controlled individually. The most straightforward method is increasing the numbers of the driver (including the driver A, B, C and D in FIG. 1). According to the driving signals (the driving signal A, B, C and D in FIG. 1) provided by the control center 700, the single area LED array is lightened up by single driver, and the brightness in each area is controlled accurately. However, the volume, weight and cost of the system are increased enormously by the method thereof.
Please refer to FIG. 2, which is a circuit diagram showing another area control driving circuit of the LED backlight lamp according to the prior art. It is configured by the backlight module 100, the control center 700, and an additional independent driver 300. The difference between FIG. 2 and FIG. 1 lies in that the backlight lamp in each area serially connected to an active power switch (including the switch A, B, C and D in FIG. 2) is only needed. According to the signals (the driving signal A, B, C and D in FIG. 2) provided by the control center 700, the pulse width modulation (PWM) control is achieved individually by each active power switch in order to realize the emitting method of the area control. The active power switch is substituted for the drivers in each area, and the volume, weight and cost of the system must be decreased. However, the impedance of each LED has some differences. Therefore, if the area control is achieved by the driving method, the driving currents of each LED array are not identical. At present, each active power switch serially connected to a linear regulator (not shown) is the general solution in order to achieve the function of stabilizing current. However, too much electricity power are consumed by the linear regulator and the systematic efficiency is decreased.
It is therefore attempted by the applicant to deal with the above situation encountered in the prior art.